The present invention relates to a coating composition for ink-receiving layer formation improved in the fixability and water resistance of inks and a process for producing the same. More particularly, this invention provides a coating composition which, when applied to a substrate such as, e.g., a plastic film, synthetic paper knitted or woven fabric, nonwoven fabric, paper, or metal, gives an ink-receiving layer satisfactory in printability and the fixability and water resistance of inks in ink-jet printing, and further provides a process for producing the composition.
Ink-jet recording is much utilized recently in various facsimile telegraphs and printers because of its advantages, for example, that high-speed recording is possible, that the impact noise is slight because the printing head does not come into contact with the printing substrate, that various printing substrates including plain paper are usable, and that color recording is possible.
The printed images are required to be high-contrast clear images free from ink running. Because of this, in the case where a printing substrate other than paper, such as a plastic film or synthetic paper, is used, an ink-receiving layer is formed on a surface of the substrate by coating. An ink-receiving layer is required to quickly absorb an ink, fix the absorbed ink, and impart water resistance to the print surface.
Ink-receiving layers have been proposed which contain a cationic compound as an ink fixative so as to meet those requirements. For example, a recording medium comprising a poly(vinyl acetal) resin and a cationic compound as essential components is proposed in Unexamined Published Japanese Patent Application 7-61113. Furthermore, an ink-receiving layer comprising a mixture of poly(vinyl alcohol), polyvinylpyrrolidone, and a vinyl acetate homopolymer and/or a vinyl acetate copolymer and, incorporated in the mixture, a quaternary ammonium compound is proposed in Unexamined Published Japanese Patent Application 7-68926.
However, the above-described techniques still have unsolved problems concerning ink running, etc. attributable to insufficient adhesion to the printing substrate and the insufficient water resistance of the film. In addition, no ink-receiving layer has been obtained so far which is fully satisfactory in ink drying property.
An object of the present invention is to obtain a coating composition eliminating the problems described above and giving an ink-receiving layer for ink-jet recording which is satisfactory in transparency, ink absorbing properties, and the fixability and water resistance of inks.
The present inventors made intensive studies in order to eliminate the above-described problems and, as a result, have achieved the present invention.
The present invention discloses a coating composition for forming an ink-receiving layer showing satisfactory ink absorbing properties, enabling the formation of clear images free from ink running, and excellent in the fixability and water resistance of inks, which comprises: an anionic graft polymer (1) obtained by graft-polymerizing (C) from 100 to 60 wt % at least one hydrophilic radical-polymerizable vinyl monomer and from 0 to 40 wt % other copolymerizable vinyl monomer(s) in an aqueous solution or dispersion comprising a mixture of (A) from 100 to 10 wt % water-compatible polyester resin having an average molecular weight of from 4,000 to 30,000 and from 0 to 90 wt % aqueous urethane resin and (B) a poly(vinyl alcohol) having a degree of saponification of from 75 to 100% and a degree of polymerization of from 500 to 5,000; and a modified cationic polymer (2) obtained by mixing (D) a copolymer of from 10 to 100 wt % at least one radical-polymerizable vinyl monomer having a cationic quaternary ammonium salt group as a side chain and from 90 to 0 wt % other copolymerizable vinyl monomer(s) with (E) a poly(vinyl alcohol) having a degree of saponification of from 75 to 100% and a degree of polymerization of from 500 to 5,000. The present invention further discloses a process for producing the coating composition.
It is generally known that in ink-receiving layers for ink-jet recording, enhanced ink absorbing properties result in reduced water resistance and, conversely, improved water resistance results in reduced ink absorbing properties and impaired ink drying properties to arouse problems such as reduced image quality due to ink running or beading.
In order to eliminate such problems, the present inventors previously proposed the formation of an ink-receiving layer having a two-layer structure composed of anionic and cationic layers. However, the inventors have lately found that the properties of the two-layer structure can be attained with a single fluid. The present invention has been achieved based on this finding.
The composition of the present invention is a coating composition which is a single fluid wherein the anionic polymer in which a hydrophilic vinyl monomer has been graft-polymerized coexists with the cationic polymer surrounded by a poly(vinyl alcohol).
The present invention will be explained below in detail.
The water-compatible polyester resin used in the present invention is a polyester resin having an average molecular weight of from 4,000 to 30,000.
The water-compatible polyester resin for use in the present invention may be produced by subjecting a dicarboxylic acid and a diol to esterification (transesterification) and polycondensation by a known production technique. However, methods for this production should not be limited in any way.
The dicarboxylic acid ingredient preferably consists mainly of an aromatic dicarboxylic acid, such as terephthalic acid, isophthalic acid, phthalic acid, or naphthalenedicarboxylic acid, or of an ester thereof. This is because use of such dicarboxylic acids has an advantage that the aromatic nuclei of the acids have a high affinity for hydrophobic plastics to thereby improve adhesiveness. In particular, a water-compatible polyester resin produced from terephthalic acid shows tenacious adhesion to molded objects of poly(ethylene terephthalate) type polyesters and is hence a preferred water-compatible polyester resin.
An aromatic dicarboxylic acid such as those shown above or an ester thereof is preferred as the dicarboxylic acid ingredient used for forming the water-compatible polyester resin for use in the present invention. However, an aliphatic dicarboxylic acid such as adipic acid, succinic acid, sebacic acid, or dodecanedioic acid, an alicyclic dicarboxylic acid such as cyclohexyldicarboxylic acid, a hydroxycarboxylic acid such as hydroxybenzoic acid, or an ester of any of these acids may be used, besides those aromatic ingredients, as the dicarboxylic acid ingredient or as a part thereof.
In the case of using an ester, it is a lower-alkyl ester, e.g., a methyl ester or ethyl ester. These esters may be monoesters or diesters.
On the other hand, the diol ingredient to be used may be ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, or a bisphenol.
The water-compatible polyester resin of the present invention is produced through polymerization in such a manner that the molecule thereof contains sulfonic salt groups or carboxylic salt groups as hydrophilic groups so as to impart water solubility or water dispersibility to the resin.
Examples of techniques for incorporating a sulfonic salt include a method in which a dicarboxylic acid component such as, e.g., a 5-sodiumsulfoisophthalate is used as part of the dicarboxylic acid ingredient. The use amount thereof is preferably from 2 to 15 mol % based on the dicarboxylic acid ingredient.
Examples of techniques for incorporating a carboxylic salt include a method in which a polyester containing a carboxylic acid is prepared, for example, by using a polycarboxylic acid containing three or more carboxyl groups as an acid ingredient to be condensed in polyester resin production or by grafting a polymerizable unsaturated carboxylic acid onto a polyester resin, and the polyester containing a carboxylic acid is converted to a salt with a substance forming water-soluble salts together with an alkali metal, any of various amines and ammonium compounds, or the like.
The amount of the carboxylic salt in the polyester resin is preferably in the range of from 15 to 250 KOH-mg/g in terms of the acid value of the polyester resin yielded.
The molecular weight of the water-compatible polyester resin of the present invention is from 4,000 to 30,000 as stated hereinabove. If the molecular weight thereof is below 4,000, resin properties such as water resistance, blocking resistance, and adhesiveness are reduced. If the molecular weight thereof exceeds 30,000, it is difficult to evenly dissolve or disperse the resin in water and the resultant composition tends to gel with the lapse of time.
An especially preferred water-compatible polyester resin has a molecular weight of from 5,000 to 25,000.
The water-compatible polyester resin of the present invention is dissolved or dispersed in water. In the case of a polyester resin containing a sulfonic acid salt, this resin is dissolved or dispersed with stirring in water preferably having
a temperature of from 50 to 90xc2x0 C. In this case, a water-soluble organic solvent maybe used in order to facilitate the dissolution or dispersion of the resin. Examples of the water-soluble organic solvent include lower alcohols, polyhydric alcohols, and alkyl ethers or alkyl esters thereof. Specifically, use can be made of lower alcohols such as methanol, ethanol, n-propanol, and isopropanol, polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and glycerol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol acetate, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and the like.
In the case of a polyester resin containing a carboxylic acid salt, this resin is dissolved or dispersed with stirring in water containing an alkaline compound, e.g., ammonia water, sodium hydroxide, potassium hydroxide, or any of various amines, and preferably having a temperature of from 50 to 90xc2x0 C. In this case also, a water-soluble organic solvent such as those enumerated above may be used.
The aqueous urethane resin for use in the present invention is one obtained by dissolving or dispersing in water a polyurethane resin synthesized from a polyhydroxy compound, a diisocyanate, and a low-molecular weight chain extender containing at least two hydrogen atoms reacting with the diisocyanate. It can be synthesized by a known method. The polyurethane resin means one having in the molecule anionic groups e.g, carboxyl groups, as hydrophilic groups which enable the resin to be dissolved or dispersed in water.
Examples of the polyhydroxy compound used for the urethane resin production include polyester polyols obtained by the dehydrating condensation reaction of an organic acid, e.g., phthalic acid, adipic acid, linoleic acid dimer, or maleic acid, with a glycol, e.g., ethylene glycol, propylene glycol, butylene glycol, or diethylene glycol, trimethylolpropane, hexanetriol, glycerol, trimethylolethane, pentaerythritol, or the like, polyoxypropylene glycol, polyoxybutylene glycol, polytetramethylene glycol, polyoxypropylene triol, polyoxyethylene-polyoxypropylene triol, sorbitol, pentaerythritol, sucrose, starch, polyether polyols produced with an inorganic acid, e.g., phosphoric acid, as an initiator, such as polyoxypropylene polyols and polyoxypropylenepolyoxyethylene polyols, acrylic polyols, castor oil derivatives, tall oil derivatives, and other hydroxylated compounds.
Examples of the diisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4xe2x80x2-diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, 4,4xe2x80x2-dicyclohexylmethane diisocyanate, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-biphenylene diisocyanate, 3,3xe2x80x2-dimethoxy-4,4xe2x80x2-biphenylene diisocyanate, 3,3xe2x80x2-dichloro4,4xe2x80x2-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, and 1,5-tetrahydronaphthalene diisocyanate.
Examples of the chain extender include polyols such as ethylene glycol, 1,4-butanediol, trimethylolpropane, triisopropanolamine, N,N-bis(2-hydroxypropyl)aniline, hydroquinone bis(xcex2-hydroxyethyl) ether, and resorcinol bis(xcex2-hydroxyethyl) ether, polyamines such as ethylenediamine, propylenediamine, hexamethylenediamine, phenylenediamine, tolylenediamine, diphenyldiamine, diaminodiphenylmethane, diaminodiphenylmethane, diaminodicyclohexylmethane, piperazine, isophoronediamine, diethylenetriamine, and dipropylenetriamine, hydrazine and analogues thereof, and water.
The poly(vinyl alcohol) for use in the present invention preferably is one which is obtained generally by saponifying poly(vinyl acetate) by the acid saponification method or alkali saponification method and has a degree of saponification of from 75 to 100%. The poly(vinyl acetate) may be a copolymer with up to 5% other copolymerizable monomer(s).
A poly (vinyl alcohol) having a degree of polymerization of from 500 to 5,000 is preferred. A mixture of poly(vinyl alcohol)s differing in degree of polymerization or degree of saponification may be used.
The hydrophilic radical-polymerizable vinyl monomer for use in the present invention may be a monomer having a hydrophilic group represented by any of the following chemical formulae. 
In the above formula, xe2x80x94R is xe2x80x94H or xe2x80x94CH3.
(b) xe2x80x94COOX
In the above formula, X is H, an alkali metal, or an amine. 
In the above formula, xe2x80x94R is H or CH3, and n is a positive integer. 
In the above formula, xe2x80x94Yxe2x80x94 is 
or xe2x80x94CH2xe2x80x94 and xe2x80x94R1 and xe2x80x94R2 each is xe2x80x94H, xe2x80x94CH3, xe2x80x94C2H5, xe2x80x94CH(CH3)2, xe2x80x94CH2OH, xe2x80x94C(CH3)2xe2x80x94(CH2)nxe2x80x94A, or xe2x80x94(CH2)mxe2x80x94B, provided that n is 1 or 2; m is 2 or 3; A is xe2x80x94SO3D, xe2x80x94COCH3, xe2x80x94N(CH3)2, or xe2x80x94N+(CH3)3Clxe2x88x92; D is xe2x80x94H or an alkali metal salt; and B is xe2x80x94N(CH3)2 or xe2x80x94N+(CH3)3Clxe2x88x92, and that R1 and R2 may be bonded to each other to form a heterocyclic ring. 
In the above formula, xe2x80x94R3, xe2x80x94R4, and xe2x80x94R5 each is xe2x80x94CH3 or xe2x80x94C2H5. 
Specific examples of the hydrophilic radical-polymerizable vinyl monomer for use in the present invention include hydroxylated acrylic esters such as hydroxylethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate, glycol esters such as ethylene glycol acrylate, ethylene glycol methacrylate, polyethylene glycol acrylate, and polyethylene glycol methacrylate, acrylamide compounds such as acrylamide, methacrylamide, methylolacrylamide, and methoxymethylolacrylamide, glycidyl acrylate compounds such as glycidyl acrylate and glycidyl methacrylate, nitrogen-containing vinyl compounds such as vinylpyridine, vinylimidazole, and vinylpyrrolidone, unsaturated acids such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, and crotonic acid and salts of these acids, aminoalkyl acrylates, and aminoalkyl methacrylates.
The above hydrophilic radical-polymerizable monomers may be used alone or as a combination of some of these. A combination of any of these hydrophilic monomers with one or more other vinyl monomers copolymerizable therewith may also be used.
Examples of those other copolymerizable vinyl monomers include vinyl esters such as vinyl acetate and vinyl propionate, vinyl halides such as vinyl chloride and vinyl bromide, esters of unsaturated carboxylic acids, such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate, vinylsilanes such as dimethylvinylmethoxysilane and xcex3-methacryloxypropyltrimethoxysilane, and olefin and diolefin compounds such as ethylene, propylene, styrene, and butadiene.
The anionic graft polymer for use in the present invention is obtained by graft-polymerizing from 100 to 60 wt % at least one hydrophilic radical-polymerizable vinyl monomer and from 0 to 40 wt % other copolymerizable vinyl monomer(s) with an aqueous solution or dispersion comprising a mixture of from 100 to 10 wt % the water-compatible polyester resin, from 0 to 90 wt % the aqueous urethane resin, and a poly(vinyl alcohol).
By varying the proportion of the water-compatible polyester resin to the aqueous urethane resin, films having satisfactory adhesiveness to various bases can be formed. Proportions of the water-compatible polyester resin below 10 wt % are undesirable in that light resistance, heat resistance, and the adhesion of pigment inks are impaired.
Proportions of the hydrophilic vinyl monomer below 60 wt % are undesirable in that ink absorbing properties are impaired.
In conducting polymerization for obtaining the anionic graft polymer, a conventionally known method can be used. Examples thereof include a method which comprises adding a polymerization initiator and, if desired, a small amount of an emulsifying agent to an aqueous dispersion comprising a mixture of from 100 to 10 wt % the water-compatible polyester resin and from 0 to 90 wt % the aqueous urethane resin with a poly(vinyl alcohol), gradually adding the radical-polymerizable vinyl monomer thereto while holding the dispersion at 70 to 80xc2x0 C. with stirring, and then aging the reaction mixture for from 2 to 5 hours to complete the polymerization and thus obtain the anionic graft polymer of the present invention. The radical-polymerizable vinyl monomer graft-polymerizes with the water-compatible polyester resin, aqueous urethan resin, and poly(vinyl alcohol) Consequently, this ingredient has not only excellent ink absorbing properties but properties characteristics of polyester resins and polyurethane resins, such as adhesiveness, water resistance, and toughness.
As the polymerization initiator can be used a general radical polymerization initiator. Examples thereof include water-soluble peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide, oil-soluble peroxides such as benzoyl peroxide and t-butyl hydroperoxide, and azo compounds such as azodiisobutyronitrile.
The proportions of the poly(vinyl alcohol) and the radical-polymerizable vinyl monomer to the water-compatible polyester resin or to a mixture of the water-compatible polyester resin and the aqueous urethane resin are such that the amount of the poly(vinyl alcohol) is from 10 to 500 parts by weight, preferably from 20 to 300 parts by weight, and that of the radical-polymerizable vinyl monomer is from 10 to 500 parts by weight, preferably from 20 to 300 parts by weight, per 100 parts by weight of either the water-compatible polyester resin or the water-compatible polyester resin/aqueous urethane resin mixture on a solid basis.
If the amount of the poly (vinyl alcohol) is below 10 parts by weight, image clearness and ink absorbing properties are impaired. If the amount thereof exceeds 500 parts by weight, water resistance and the adhesiveness of pigment inks are impaired On the other hand, if the amount of the radical-polymerizable vinyl monomer is below 10 parts by weight, ink absorbing properties are impaired. If the amount thereof exceeds 500 parts by weight, water resistance and blocking resistance are impaired.
Examples of the radical-polymerizable vinyl monomer having a cationic quaternary ammonium salt group as a side chain which is used in the present invention include monomers having a quaternary ammonium salt group, such as quaternized aminoalkyl acrylates or methacrylates, e.g., dimethylaminoethyl methacrylate quaternized with methyl chloride or dimethylsulfuric acid, dimethylaminopropyl(meth)acrylamide quaternized with methyl chloride, dimethylsulfuric acid, benzyl chloride, monochloroacetic acid, or the like, quaternized acrylamido-3-methylbutyldimethylamines, vinylbenzylammonium salts, and diallylammonium salts.
Usable examples of other vinyl monomers copolymerizable with the radical-polymerizable vinyl monomer having a cationic quaternary ammonium salt group as a side chain are the same as those enumerated hereinabove.
In the copolymer of from 10 to 100 wt % the radicalpolymerizable vinyl monomer having a cationic quaternary ammonium salt as a side chain and from 90 to 0 wt % other copolymerizable vinyl monomer(s) (hereinafter referred to as xe2x80x9ccationic copolymerxe2x80x9d), if the content of the radical-polymerizable vinyl monomer having a cationic quaternary ammonium salt as a side chain is below 10 wt %, ink fixability and ink absorbing properties are impaired.
Examples of methods usable for obtaining the cationic copolymer include conventionally known methods. For example, the cationic copolymer can be obtained by dissolving a polymerization initiator and, if desired, a small amount of an emulsifying agent in water, gradually adding the radicalpolymerizable vinyl monomer dropwise thereto while holding the solution at 70 to 80xc2x0 C. with stirring, and then aging the reaction mixture for from 2 to 5 hours to complete the polymerization.
Usable as the polymerization initiator are peroxides such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide and azo compounds such as azodiisobutyronitrile and 2,2xe2x80x2-azobis(amidinopropane) dihydrochloride. Initiators which generate an anionic group, such as potassium persulfate and ammonium persulfate, are undesirable in that the anionic group forms a complex with a cationic monomer.
The cationic copolymer of the present invention has so high film-forming properties that it forms a transparent film upon drying at temperatures not lower than 0xc2x0 C. The copolymer forms an ion complex with the anionic dye contained in an ink and thus shows an excellent ink-fixing properties.
The modified cationic polymer for use in the present invention is obtained by mixing the cationic copolymer described above with a poly(vinyl alcohol). This poly(vinyl alcohol) can be the above-described one having a degree of saponification of from 75 to 100% and a degree of polymerization of from 500 to 5,000. The surface of the cationic copolymer of the present invention comes to be nonionic upon mixing beforehand with a poly(vinyl alcohol), so that the resultant modified cationic polymer does not readily form an ion complex with the anionic graft polymer of the present invention and can hence be present stably.
The mixing ratio of the cationic copolymer to the poly(vinyl alcohol) is such that the amount of the poly(vinyl alcohol) is from 5 to 200 parts by weight per 100 parts by weight of the cationic copolymer on a solid basis. If the amount of the poly (vinyl alcohol) is smaller than 5 parts by weight, mixing with the anionic graft polymer is impossible. If the amount of the poly (vinyl alcohol) exceeds 200 parts by weight, ink fixability, adhesion to substrates, and adhesion of pigment inks are impaired.
The coating composition for ink-receiving layer formation of the present invention is obtained by mixing the anionic graft polymer with the modified cationic polymer. Although methods for mixing are not particularly limited, the most stable coating fluid can be prepared by a method in which an aqueous dispersion of the anionic graft polymer is gradually dropped into an aqueous dispersion of the modified cationic polymer. In the coating fluid prepared by this method, the anionic graft polymer and the cationic polymer never form an ion complex to yield coagulates, and can be stably present. The reason for this may be as follows. Since the anionic polyester resin particles or the urethane resin particles are protected by the grafted polymer and the cationic copolymer also is surrounded by the Poly (vinyl alcohol), both resins independently coexist as fine particles in the same liquid without undergoing adsorption or coagulation. It is thought that after drying and film formation, the film has a sea-island structure in which the cationic ingredient having ink-fixing properties is present as fine particles in the ink-absorbing ingredient. The above can be understood from the fact that this film has far more improved adhesiveness to substrates and water resistance than separately formed films.
The mixing ratio of the anionic graft polymer to the modified cationic polymer is from 50:50 to 95:5 by weight on a solid basis. If the proportion of the modified cationic polymer exceeds 50 wt %, not only printing failures occur in printing with dye type inks but the water resistance and fixability of the inks are impaired. Moreover, such a high proportion of the modified cationic polymer is causative of the curling of polyester film or other substrates after drying. If the proportion of the modified cationic polymer is below 5 wt %, ink fixability is insufficient and water resistance is impaired.
Optional ingredients may be added according to need to the thus-obtained coating composition for ink-receiving layer formation of the present invention. Examples thereof include resin ingredients such as epoxy resins, amino resins, acrylic resins, polyester resins, and urethane resins, crosslinking agents such as isocyanate compounds, epoxy compounds, carbodiimide, and silane coupling agents, inorganic fillers such as silica, alumina, talc, kaolin clay, calcium carbonate, andmica, organic fillers such as fine porous particles of poly(methyl acrylate), polystyrene, or polyacrylonitrile, inorganic and organic pigments such as titanium and chromium compounds, and conventionally known additives such as film-forming aids, thickening agents, leveling agents, antiblocking agents, antistatic agents, ultraviolet absorbers, and antioxidants.
The coating composition for ink-receiving layer formation of the present invention is applied to a substrate, which will be described below, and dried.
Usable as the substrate is a molded object, e.g., a plastic film, or a printing paper, e.g., a synthetic paper. Examples of the plastic film include films of polyesters, polyethylene, polypropylene, PVC, polycarbonates, nylons, polystyrene, cellophane, and triacetate, while examples of the synthetic paper include ones made of polypropylene, polyethylene, polystyrene, and polyesters. It is also possible to apply the composition to paper, textiles such as woven and knitted fabrics, nonwoven fabrics, metals, woods, ceramics, molded articles such as earthenwares, etc.
The coating composition for ink-receiving layer formation of the present invention is generally used in the form of a solution or dispersion based on water or based mainly on water. The concentration thereof is preferably from 10 to 50 wt %. The composition is applied on one or both sides of a printing substrate with an ordinary roll coater, gravure coater, bar coater, knife coater, or the like and dried. The application amount thereof is generally from 2 to 50 xcexcm, preferably from 5 to 30 xcexcm, in terms of film thickness after drying. In the case of textiles, nonwoven fabrics, or the like, the processing may be conducted by dipping.
Usable printing inks in ink-jet printing on the ink-receiving layer are water-based and oil-based dye inks and pigment inks. In actual ink-jet printing, ink drops ejected from a nozzle strike on the ink-receiving layer and are absorbed by the layer. An acid dye or pigment in the ink ingredients is fixed by the cationic copolymer contained in the receiving layer. As a result, the ink-receiving layer thus obtained shows satisfactory adhesion to the substrate, is satisfactory in transparency and gloss, and is excellent in the absorption and drying of inks. The image recorded thereon by ink-jet recording is clear and free from ink running and is satisfactory in the fixability and water resistance of the ink. The printed substrate further has satisfactory storage stability.
The coating composition does not necessitate addition of a crosslinking agent or the like thereto, and can basically be used as the single fluid. Since merely applying and then drying the composition enables the resultant film to exhibit the performances described above, a considerable saving of coating cost is attainable. Therefore, the coating composition is useful for forming ink-receiving layers for use in the above application.
The present invention will be explained below in more detail by reference to Examples.